but in some places it has, in its sluggish course, pushed the rubble
before it until a great heap has accumulated, when either it has
broken through the mass and continued its course underneath, or
poured over it in order to resume its way on the other side. An
instance of this is to be seen to the south of Ladder Hill signal station*
where an immense accumulation of rubble has been forced forward
by the huge stream of lava overlying Pierie’s Eevenge. In some o
the earliest, as well as the l a t e s t of these beds, there exist cylindrical
holes, which are now quite empty, but close examination removes
almost any doubt as to their o n c e h a v i n g .been filled by stems of
trees. I t is most improbable that trees grew upon any part ol the
-Island at that period when the rubble beds were being formed and
whether the stems embedded in themgre w on some near adjacent land,
or were floated from some distant country across the sea and through
the agency of currents into the crater, cannot now be determined,;,
but the latter theory seems very probable because m the present day
seeds of plants which grow eastward of the Cape of Good Hope are
conveyed and cast up by the sea on to Sandy Bay Beach, the very
centre of the crater. Had these stems been enveloped m the lava
they would have been quickly burnt; this may have occurred with
some of them of which no trace now remains, hut it seems most
probable that they would be cast out of the crater with the
rubble before the ejection of lava commenced; and we thus find
them in these beds. The heated rubble would suffice to burn
the wood, converting it into carbon, which in conjunction with
steam and other gases would easily cause its disappearance m the
form of carbonic acid gas, &c., so that, while the rubble would have
sufficiently hardened to retain a cast of the external shape of the
stem no trace of the tree itself would remain. Possibly, remains of
the wood ma3 yet be found in some newly-opened cast. I have
only seen those which have been long ago cut through m making
roads when perhaps if they contained anything it was, never noticed.
Although no remains of the original wood were to be seen m those
which I examined, there was no difficulty m tracing, on the side of
the casts, an imprint of the coarsely imbricated form of the stem,
showing it to have borne the characteristics of a palm or large
tr66 fern
A vei-y complete cast of this kind, which measures nine inches
in diameter and forty-two inches in length, occurs m one of the
earliest rubble beds, and may be seen on the western side of “ The
Shy Path,” opposite to the storehouse called “ California in Jamestown.
Another occurs in a bed of more recent formation, six hundred
feet or more higher up on the .same hillside, just behind the
observatory on Ladder Hill. And in various parts of the Island
others, in a more or less perfect state, are to be seen.
The lava beds which follow on the rubble, and of which, as already
stated, at least sixty or seventy may be easily counted, vary so much
more in composition than' either the mud or the rubble that more
time and space need to be devoted to their examination. The first
layers of lava which are seen above the sea line along the northern,
eastern, and western coasts, excepting that portion between Holdfast
Tom and Horse Point, are for the most part composed of a very dense
compact basalt, containing very few cavities; they vary in thickness
from a foot or two to ten or twenty feet. Although the cavities are
few, some of them in these lower basaltic strata contain ■ a most interesting
relic of the age when they were formed, being filled with
sea water, which through hundreds of centuries has been hermetically
sealed up in them. I discovered this one day, while looking
at the blasting of stone for the public works, in a small quarry on
the western hillside in Jamestown; during the operation, immediately
that a fresh fracture of the rock took place, a wet circle appeared
surrounding some of the little pea-shaped cavities which had been
split open by firing the blast. The water thus released from its
long imprisonment was not sufficient to admit of its being collected,
but, by a quick application of the tongue, its nauseous flavour afforded
tolerably good evidence of its really being sea water. Little were
those rough quarrymen aware of the extremely interesting fact they
were revealing in disentombing water which had existence -thousands
of years before, and which had been so carefully preserved by nature
through all that time from any change.
After several layers of this hard basaltic character, in which
either augite or felspar slightly predominate, at an altitude of two
hundred feet, the nature of the lava changes; and a single layer
of quite a different composition intervenes, viz., a very heavy dark
blue basalt, much more augitic in character than the lower basalts,
and containing embedded crystals of augite and olivine. Next in
order, above this, the layers are again simple basalt, only changed
sometimes by strata of a more felspathic nature, such as greystone